Ability

An ability defines an active, passive or triggered ability, including its resource costs, cooldown, availability condition and the behaviour it executes.

File Location

Ability files go in data/<namespace>/mxt/ability/ within your datapack.

The filename corresponds to its ID. For example, data/example/mxt/ability/fireball.json has the ID example:fireball.

Fields

Field	Type	Default	Description
ability	AbilityType object	required	Built-in ability type object; the object must contain a type dispatch key.
costs	List<ResourceCost>	[]	Resources deducted before the ability executes.
cast_time	NumberProvider	0	Cast time.
cooldown	NumberProvider	0	Cooldown.
components	List<AbilityComponent>	[]	State components such as cooldown, charges, toggling and duration.
modifiers	List<AttributeEntry>	[]	Passive vanilla attribute modifiers; an entry contains attribute, id, amount and operation, plus an optional value formula.
damage_condition	DamageCondition	mxt:always_true	Restriction on damage triggers.
condition	EntityCondition	mxt:always_true	Condition for the ability to be usable.
entity_action	EntityAction	mxt:no_op	Behaviour executed on the caster.
target_condition	BiEntityCondition	mxt:always_true	Target relation condition.
bi_entity_action	BiEntityAction	mxt:no_op	Behaviour executed on the caster and the target.
element_affinity	HolderOrTag<element>[]	[]	Element affinity markers of the ability.

ability.type

ability.type is an extensible built-in dispatch table, mxt:ability_type, with the built-in types empty, active, triggered, modifier, aura, channelled, composite and word. Two of these types change when behaviour is executed:

Type	Exclusive Fields	Behaviour Execution Timing
mxt:channelled	tick_interval (default 1), upkeep_costs (default [])	Executes entity_action and the target behaviour once on activation, then once per tick_interval after the upkeep resources have been deducted successfully, until it is released or the upkeep fails. It is the only behaviour entry point of a sustained effect.
mxt:composite	abilities (required), all_required (default true)	Does not execute behaviour itself; with all_required: false only the first ability in the list is executed, while with true the costs of every ability are submitted in list order and then the behaviour of each child ability is executed in turn.

The effects of mxt:channelled and mxt:composite are both produced through the same set of fields: entity_action applies to the caster, target_selector and bi_entity_action apply to the selected target, while the word type is a terminal payload that does not execute target behaviour any more.

Example

{
  "ability": {
    "type": "mxt:triggered",
    "triggers": [{"type": "mxt:item_use"}]
  },
  "costs": [
    {"id": "example:qi", "amount": "10 + level"}
  ],
  "cooldown": 100,
  "condition": {"type": "mxt:sneaking"},
  "entity_action": {"type": "mxt:damage", "amount": "4 + level"}
}

A channelled ability that pays upkeep every 20 ticks:

{
  "ability": { "type": "mxt:channelled", "tick_interval": 20, "upkeep_costs": [{"id": "example:qi", "amount": 1}] },
  "entity_action": {"type": "mxt:add_resource", "resource": "example:qi", "amount": 2}
}

A top-level ability that should be a channelled ability released from the ability hotbar must use mxt:channelled as a child ability of mxt:composite: mxt:active and mxt:channelled are mutually exclusive single types, and only the child abilities of a composite ability become the active channel.

{
  "ability": { "type": "mxt:composite", "abilities": ["example:meditate_channel"] },
  "cooldown": 100
}

Server-authoritative

Numeric fields of abilities uniformly use NumberProvider. An ability must pass its condition and all resource costs before its behaviour is executed. Ability behaviour is handled on the server; the client hotbar only sends use and cancel requests.

Abilities can read the entity variables plus the ability and trigger variables (element_modifier, damage, target_health, …); see Formula Variables.